The objective of this proposal is to learn how molecular oxygen is activated by the enzymes called oxygenases. Oxygenases are found in all aerobic organisms and are important in the biosynthesis, transformation, and degradation of steroids, nucleic acid catecholaines collagen, drugs, prostaglandins, and various foreign compounds. These enzymes are therefore crucial not only to the metabolism of endogeneous substrates, but also to pharmacological and toxicological processes. We are proposing to study three different enzyme systems which catalyze oxygenation reactions: 1) Protocatechuate dioxygenase from Pseudomonas putida is an example of a nonheme iron dioxygenase which is important in the degradation of aromatic compounds by soil bacteria; 2) P-450 from hepatic microsomes is an example of a hemoprotein monooxygenase and is important in the detoxification processes of the liver; 3) Amine oxidase, also from hepatic microsomes, is an example of a flavorprotein monooxygenase which participates in the metabolism of numerous drugs and may be involved in the formation of disulfide bridges in proteins. All of these enzymes can be isolated in homogeneous form. Each of these enzymes has a unique prosthetic group; all nevertheless catalyze similar oxygenation reactions. The proposed studies will involve physical measurements using rapid reaction and low temperature techniques to characterize complexes of these purified enzymes with oxygen. It is hoped that a thorough chemical characterization of the oxygenated complexes of several different classes of enzymes will lead to general principles of the activation of oxygen in biological processes.